One of the world’s most invasive aquatic plants is now in DuPage County, much to the concern of researchers and state officials. But they said the discovery underscores how public education can keep this invasive species and others out of Illinois waterways.
Hydrilla, an aquatic plant native to Europe and Asia, was discovered in October in Oak Brook. It’s a prolific grower, experts said, requiring little light or nutrients. As a result, hydrilla “explosions” can decimate local ecosystems and the economies that depend on clear waterways.
“It’s bad for everything,” said Greg Spyreas, a botanist with the Illinois Natural History Survey.
Cold winter temperatures won’t stop hydrilla growth, either. The plant can survive at the bottom of lakes that typically don’t freeze in the winter.
This is the second time hydrilla has been discovered in Illinois since 2019, according to the U.S. Geological Survey. The first time, the aquatic plant was eradicated quickly after being found in a pond where output to the Des Plaines River could be easily monitored.
But the current situation is worse, said Claire Snyder, a natural resources specialist who works with aquatic invasive species at the Illinois Department of Natural Resources.
Ginger Creek in Oak Brook is connected to other bodies of water so there’s a high chance that hydrilla has spread. “The system does not exist in a little bubble,” Snyder said. The department hasn’t yet detected hydrilla in the nearby Salt Creek.
The IDNR suspects hydrilla could have been unintentionally dumped by someone with a home aquarium or garden pond. Hydrilla is a popular plant for many in this space for some of the same reasons it’s considered highly invasive.
Hydrilla and the aquarium hobby
Bailin Shaw, president of the Chicago Aquatic Plant Society, visits family and friends in the South often, where he’s seen ponds and lakes overtaken by hydrilla. In many southern states, hydrilla has been in waterways for decades.
“Until you’ve seen a pond completely covered by it, it’s hard to understand what kind of impact that makes,” he said.
Hydrilla remains popular among aquarium hobbyists because of how quickly it can grow.
“It’s used kind of in cleaning up water, it’s a nutrient sponge in a lot of ways. It’s a great medium for spawning fish. It grows quickly, it’s a great spot for baby fish to hide,” Shaw said. “But that is a problem.”
Although hydrilla is illegal to buy, sell or transport in Illinois, you can still find it at some local aquatic plant nurseries or stores, Shaw said. It’s also common at fish swaps, when members of different clubs will trade live fish or aquatic plants.
There’s a need for education around this plant and other invasive species, Shaw said. Hobbyists are largely unaware of how to identify the plant and how quickly it can become a problem outdoors.
Suppliers and stores that sell it are also responsible, Shaw said. Despite hydrilla being illegal, regulations aren’t always enforced, especially when it’s a popular seller. “Because of the ability to make the money off of this, they kind of overlook that it’s a pervasive problem.”
The Chicago Aquatic Plant Society plans to give presentations to their members on the dangers of hydrilla and other invasive species next month. They’ll also include information on their website and social media.
Every month, over 50 fish and bird vendors selling animals, plants and other supplies meet at the Fins & Feathers Fest in Mount Prospect. At this month’s event, organizer Adam Columbus said while there wasn’t any hydrilla, there were plenty of conversations about it.
“Everyone has different pieces, I guess, of a little bit of knowledge of (hydrilla), but no one knew the full details of it,” Columbus said. He has never seen hydrilla at other vendor events in the area, either.
Columbus said some people had heard about an invasive plant found in a nearby suburb while others were aware of hydrilla but didn’t know it was invasive. After Sunday’s fest, Columbus said it was clear the community needs more information about the dangers of hydrilla.
“The only thing to do is to keep spreading the word about it and let people know about what it is, and then maybe even also research alternatives,” he said.
Bob Sturnfield, president of the Chicago Livebearer Association, recommends the plant elodea as an alternative. It’s the North American native equivalent to hydrilla and good for cleaning the water in a tank.
But the bottom line is that “nothing from a home aquarium should ever be dumped into a local waterway or storm sewer, invasive or not,” Sturnfield said.
What makes hydrilla so invasive
Hydrilla can thrive in many environments such as lakes, rivers, wetlands and ponds. The long, weedy tendrils will grow the most during the summer, using up all the oxygen in a lake and outcompeting native plants, Spyreas said. Hydrilla invasions can prevent sunlight from reaching other plants at the bottom of ponds, for example.
After hydrilla use up all the oxygen in a lake, there will be a mass die-off. The decaying plant material becomes a feast for the microorganisms at the bottom of the lake, who also experience rapid population growth and decline.
The drastic changes in nutrient dynamics and water quality affects the ecosystem plants and wildlife, like spreading fatal disease to bald eagles.
“An ecosystem cascade happens where (hydrilla) grows so fast, outcompetes everything else, and then sort of changes the fundamental nature of the aquatic ecosystem that’s a detriment to everything, plants, animals, you name it,” Spyreas said.
Hydrilla can spread via tiny tubers, like potatoes. The tubers will end up in the sediment banks at the bottom of waterways and can regrow even if the aboveground parts of the plant are destroyed.
The plant also can grow rapidly from just a fragment. A whole new plant can grow from just a single node.
“This is fine-tooth comb kind of stuff,” said Valerie Sivicek, a botanist with the Illinois Natural History Survey. “It’s a small plant, and little fragments of it can quickly become a new invasion or take back over in the original invasion.”
Water currents or flooding can move the fragments downstream. But it’s the unaware humans transporting their boats, fishing equipment or even wet boots between waterways that concern researchers the most.
Luckily, surrounding Midwest states have dealt with hydrilla issues in the past, providing a template for the best management practices that Snyder and her team can use.
Managing the invasive plant involves using herbicides that only target hydrilla. Then, department staff will regularly survey and monitor nearby waterways for the plant. It’s a process that won’t end with a single treatment but will take years, Snyder said.
How to help
Snyder with the IDNR said that hydrilla is a problem for anyone who uses Illinois waterways. “Waterways connect all of us,” she said. “If not by actual water body connections, then by the way that people use them and recreate and fish in them.”
The IDNR recommends the following to prevent the spread of hydrilla:
- Remove all plants, animals and mud from any equipment used in bodies of water.
- Drain all water from boats and gear.
- Dry everything thoroughly with a towel or heat.
- Do not dispose of plants or animals from aquariums or water gardens in local bodies of water.
- Anyone who suspects they have identified hydrilla should notify the IDNR Aquatic Nuisance Species Program at dnr.ans@illinois.gov
